Braun tube with synchronizing electrode



HANNS-HEINZ WOLFF BRAUN TUBE WITH SYNCHRONIZING ELECTRODE Filed Nov. 24, 1956 April 9, 1940.

Patented Apr. 9, 1940 PATENT OFFICE BRAUN TUBE WITH sYNcHRoNIzING ELEoTRoDE Hanns-Heinz Wolff, Berlin, Germany, assignor, by mesne assignments, to Loewe Radio, Ine., a corporation of New York v Application November 24, 1936, Serial No. 112,488 In Germany November 25, 1935 Claims.

The invention relates to a method of and means for generating synchronization impulses for television transmissions with Braun tubes at the transmission end, whether according to the ikonoscope principle or according to any other image transmission principle in which a cathode ray scans an image surface at the transmission end.

Methods of synchronization in respect of tele- 10 vision arrangements of the type characterised have already been proposed in which the cathode ray itself initiates an electrical impulse at the end of the cell or image by the fact that it impinges on a special electrode provided adjacent the edge of the image.

It has been foundk that in this method difiiculties are encountered in obtaining impulses of suiiicient sharpness. 'I'he subject matter of the invention consists in a method of and means by which this' difficulty isoVercome. According to the invention, the cathode ray, at the edge of the image or at both edges of the image in the direction towards which the scanning movements proceed, is conducted not directly on to ,an auxiliary electrode, but through a diaphragm having a preferably very narrow slot-like aperture which is disposedy parallel to the particular edge of the image. Behind this aperture thereris arranged an auxiliary electrode, which ris connected to a suitable electric circuit. In this circuit there is produced at the moment when the cathode ray passes the aperture in the diaphragm an electric impulse of `considerable sharpness, which is amplified in the manner known per se andmay be modulated on to a carrier wave, for example the same wave on which the impulses pertaining to the contents of the image are transmitted, to be used for synchronizing the scanning of the image at the receiving end.

The invention will be described more fully in conjunction lwith the drawing. Of this,vFigs. 1 to 6 show arrangements according to the invention in section, whilst Fig. 7 illustrates an arrangement according to the invention in plan.

Fig. 1 shows a possible form `of embodiment'of the arrangement according to the invention, i1- lustrated diagrammatically as regards its position and connection in relation to the system of a Braun tube.

Fig. 2 shows a particular form of embodiment of the diaphragm provided in accordance with the invention. v v

Figs. 3a and 3b show further possible relative positions of the diaphragm, the auxiliary electrode and the image screen.

(Cl. Z50-150) Fig. 4 shows an arrangement in which the diaphragm is arranged on the base of the image screen, and f Fig. 5 an arrangement in which the auxiliary electrode is arranged on the base of the image .5. screen.

Fig. 6 shows an arrangement, in which screen-v ing means are provided in the arrangement according to the invention for the purpose of avoiding detrimental interference.

Fig. 7 shows in plan an arrangement accord ing to the invention, in which they diaphragm for the image and line synchronization are combined to form an angular diaphragm and the auxiliary electrodes for both synchronizations are u combined to form an angular auxiliary electrode.

In the drawing, l is'an anode of the cathode ray tube, and 2 and 3 are the deiiecting systems. 4 is the image screen, which may be constructed, for example, as photo-electric screen 20 or as luminous screen; its particular embodiment is not important as regards the invention. 5, 5 is the diaphragm provided according to the invention, having the aperture 6. 1 is the auxiliary electrode. 8 is the distance in the plane of the 25 image screen between the diaphragm and the image screen or between the projection of the diaphragm in the direction of the cathode ray on to the plane of the imagev screen and the image screen itself, 9 the width of the partotthe 30 diaphragm nearer to the screen, I9 the width of the slot, ll the width of the part of the diaphragm away from the screen,4 l2 the distance between diaphragm and auxiliary electrode in the direction of the cathode ray, 'and I3 the 35 width of the auxiliary electrode l. i4 and I5 are leads which are connected with the auxiliary electrode and the diaphragm respectively. it is the working resistance in respect of the auxiliary electrode, from which the synchronization im- 4o pulses are taken at the point l'l symbolised as terminal and conducted to the amplifying and/or modulating and/or transmission apparatus. I8

is the spacing between diaphragm and image screen in the direction of the cathode ray. I9 45 is the base for the image screen which, particularly in the case illustrated in Fig. 4, may be the wall of the cathode ray tube. 20 is a slot which is furnished if desired in the base for the. image screen. 2l and 22 are screening means for pre- 50 venting a detrimental interference.

It is' fundamentally possible to employ the edge of the image screen 4 itself vas the one edge of the diaphragmaperture 6, i. e., to omit the portion of the diaphragm 5 (see Fig-.12). u

Since, however, the width IB of the diaphragm aperture 6 is preferably selected to be very small for the purpose of obtaining sharp impulses, for example smaller than or equal to the width of the cathode ray in the plane of the diaphragm, the ray when impinging on the second edge of the diaphragm aperture may cause in certain circumstances interferences in the edge of the image. In these cases it is desirable in accordance with the invention to separate the diaphragm 5, 5 entirely from the image screen and to provide between the same and the image screen a spacing (which is given by the root of the square sum of the spacings designated 8 and I8), which is such that marginal interferences are safely avoided. On the other hand the distance between the edge of the image screen and the diaphragm should not be too great, as otherwise (l) spreading eiects readily occur, as a result of which the auxiliary electrode l receives interfering charges before the ray has reached the diaphragm aperture 6, and (2) (in the event of the diaphragm being situated in the same planelas the image screen, spacing 18=0) the interval of ltime between the scanning of two lines or images is unnecessarily extended. If the diaphragm is situated in a different plane to the screen, its projection in the direction of the cathode ray on to the plane of the screen may follow immediately on the screen (spacing 8=0), to that the disadvantage referred to under (2) is eliminated right from the commencement with any desired spacing between screen and diaphragm. As regards the width 9 of the ad part of the diaphragm 5 situated nearer the image screen, this for the sake of denite conditions should be greater than or equal to the thickness of the ray, but nevertheless should not be too great, in order that the scanning operations will occur in sufficiently quick succession. The width II of the edge of the diaphragm which is directed away from the image screen and is not necessarily entirely passed over by the ray may be of desired amount Within the limits given by the total construction. A lower limit in respect of I I is again provided by the necessity for avoidin;r spreading effects. It is also to avoid spreading effects that the width 43 of the auxiliary electrode 'I is made to be small and the spacing I2 in the direction of the ray between the intercepting electrode 'I and the diaphragm 5, 5' not too small. On the other hand there is an upper limit for the spacing I2 given by the dimensions of the tube, as in order to obtain impulses which are as sharp as possible the diaphragm 5, 5 is preferably arranged as far as possible away from the deflecting system 2, 3, as together with the distance there also increases the speed with which the ray passes over the aperture (i.

The elimination of spreading effects may also be accomplished in accordance with the invention by providing lateral screening means 2 I, 22, for example by constructing the entire diaphragm arrangement in the form of a practically closed casing, in the interior of which there is located the auxiliary electrode (compare Fig. 6).

In the case of an image screen arranged within the bulb of the tube the diaphragm 5, 5' may be in the same plane as the image screen (Figs. 1 and li), and in certain circumstances image screen i and diaphragm 5, 5 may be arranged with advantage on the same base I9 (Fig. 4), this being furnished to the side of the image screen with a narrow slot 20, at the sides of which there are provided on the base (for example in the form of metallic deposits) metal strips 5, 5' of a width in accordance with the above. Dependent on the general construction the diaphragm 5, 5', however, may also be disposed in a desired plane which is sufficiently remote from the deflecting system and is substantially vertical to the direction of the ray (Figs. 3a and 3b). If, for example, the image screen 4 is situated on the Wall of the tube, the diaphragm must be arranged nearer to the deiecting system than the image screen. It is also possible, particularly in the last-mentioned case, to arrange the auxiliary electrode I in the plane of the image screen, if desired on the same base (see Fig. 5), in the form of a metallic strip (for example deposit).

As shown in Fig. 6, there may be provided for the purpose of avoiding detrimental spreading effects screening means 2|, 22, which cause the electrode 'I to be touched by electrons only when the cathode ray passes over the diaphragm aperture 6. As shown in the drawing, the screening means may be combined with the diaphragm itself to form a substantially closed casing surrounding the electrode 1.

If in accordance with the invention diaphragms are provided for the line and image scanning, they may be combined in accordance with an additional feature of the invention, as shown in Fig. 7, to form an angular diaphragm element 0 and an angular synchronizing electrode. The possible arrangements according to the invention as described in conjunction with the remaining figures are capable of being applied to the arrangements in Fig. 7. and Ib may be selected of diiferent size with the object of controlling at will the impulse duration for the line and image synchronization respectively. With equal width of the slots the duration of the impulses for the image synchronization is greater than that for the line synchronization in a proportion which is given by the ratio of the scanning speeds in the two directions. Further, for the purpose of being able to control at will the ratio of the impulse amplitudes for image and line synchronization re spectively it may be desirable to insulate the parts 1a and 1b against each other and to connect the same with differently selected working resistance I 6.

The drawing is purely a diagrammatical illustration of arrangements according to the invention. Naturally it is also possible to arrange the single elements, the disposal of which in certain planes has been referred to in the above, in other,

for example cylindrical or spherical, srufaces which have a sufliciently large radius of curvature. If, for example, the image screen is arranged on the wall of the tube, its base in the majority of arrangements is approximately in the form of a spherical cup. The resistance I6, instead of being connected with the potential of the anode I, may be connected with any other desired suitably selected bias.

I claim:

l. In a cathode ray tube for television transmission comprising means for generating and deecting a cathode ray, a mosaic photo-electric screen scanned by said ray and a marginal electrode outside of and parallel to an edge of said screen for producing synchronizing signals when touched by said scanning ray, said electrode being arranged behind a shielding diaphragm the slit of which is smaller in width than said electrode.

2. In a cathode ray tube for television trans The width of slot Ila mission comprising means for generating and deflecting'a cathode ray, a mosaic photo-electric screen scanned by said ray anda marginal electrode outside of and parallel to an edge of said screen for producing synchronizing signals when touched by said scanning ray, said electrode being arranged behind a shielding diaphragm the slit of which is smaller in widththan said electrode, said diaphragm being arranged in the plane'of said screen and on the same support.

3. In a cathode ray tube for television transmission comprising means for generating and deflecting a cathode ray, an anode, a mosaic photoelectric screen, an auxiliary electrode outside of and parallelv to an edge of said screen for producing synchronizing signals When touched by said scanning ray, said electrode being arranged behinda shielding diaphragm the slit of which is smaller in Width than said electrode.`

4. In a cathode ray tube for television transmission comprising means for generating and deiiecting a cathode ray, an anode, a mosaic photoelectric screen, an auxiliary electrode outside of and parallel to an edge of said screen for producing synchronizing signals when touched by said scanning ray, said electrode being arranged behind a shielding diaphragm the slit of which is smaller in Width than said electrode, said diaphragm being `:arranged in the plane of said screen.

5. ,In a cathode ray tube for television transmission comprising m'eans for genera-ting and deecting a cathode ray, an anode, a mosaic photoelectric screen, an auxiliary electrode outside of and parallel to an edge of said screen for pro-,

ducing synchronizing signals When touched by said scanning ray,r said electrcdebeing arranged behind a shielding diaphragm the slit of which is smaller in Width than said electrode, said diaphragm being arrangedin the plane of said screen, said diaphragm and said auxiliary electrode forming right angles outside of and parallel to the adjacent edges of said screen.

6. In a cathode ray tube for television transmission comprising means for generating and deiiecting a cathode ray, a mosaic photo-electric screen scanned by said ray and an auxiliary elec-l trode outsideof and parallel to an edge of said screen for producing synchronizing signals when touched by said scanning ray, said electrode being arranged behind a shielding diaphragm the slit of which is smaller in width than said electrode,

said diaphragmA being arranged in the planer of said screen and on the same support.

'7. In a cathode ray tube for television transmission comprising means for generating and deecting a cathode ray, anr anode, a mosaic photoelectric screen,` an auxiliary velectrode outside of and parallel to an edge of said screen for producing synchronizing signals when touched by said scanning ray, said electrode being arranged behind a shielding diaphragm the slit of which f is smaller in width than said electrode, said auxiliary electrode being arranged in the plane of said screen.

8. In a cathode ray tube for television transmission comprising means for gene-rating and deflecting a cathode ray, an anode, a mosaic photoelectric screen, an auxiliary electrode outside of and; parallel to an edge of said screen for producing' synchronizing signals When touched by said scanning ray, said electrode being arranged behind a shielding diaphragm the slit of which is smaller in Width than said electrode, both said diaphragm an-d said auxiliary electrode being arranged in another plane than said screen.

9. In a cathode ray tube for television transmission comprising means for generating and deelectric screen, an auxiliary electrode outside oi and parallel to an edge of said screen for producing synchronizing signals v`when touched by said scanning ray, said electrode being arranged behind a shielding diaphragm the slit of which lis smaller in Width than said electrode, both said diaphragm and said lauxiliary electrode being f arranged in another plane than said screen, said diaphragm being extended to form a shielding casing surrounding said auxiliary electrode.

' HANNs-'HEINZ WOLFF.

' ecting a cathode ray, an anode, a mosaic photoelectric screen, an auxiliary electrode outside oi' 

